Method for pressurizing hot pulverized coal



2 Nov. 10, 1959 ALSPAUH ETAL 2,912,132

METHOD FOR PRESSURIZING HOT PULVERIZED COAL Original Filed Nov. 16, 1953INVENTORS PAUL L. ALSPAUGH ROBERT G. KEISTER & RICHARD .PERRY 49 ATTORNY Un ted W Pam O METHOD FOR PRESSURIZ'ING Hoi PULVERIZED GOAL Paul L.Alspaugh, South Charleston, Robert G. Keister, St. Albans, and RichardC. Perry, Charleston, W. Va., assignors to Union Carbide Corporation, acorporation 'of New York Original application November '16, .1953,Serial No. 392,255. Divided and this application December 29, 1958,Serial No. 783,314

2 Claims. (31. 214-152) This invention relates to a method and apparatusfor receiving hot pulverized coal at atmospheric pressure and deliveringit under pressure. into another vessel. This application claims themethod and is a division of our co-pending application Serial No.392,255, filed November 16, 1953, which claims the apparatus.

There are several methods known in the art for pressurizing granular,materials, including pulverized coal. These processes of the prior art,however, are designed for handling granular materials at normal or onlyslightly elevated temperatures. Pulverized coal'particles at atemperature of 350 C. to 400 C. present special problems in handling andno mechanism known in the art can be used successfully to pressurizecoal at these temperatures, nor can any known apparatus be readilyconverted to such use, all such apparatus being suitable only forfree-flowing materials. Throughout this specification of the inventionand the claims, the term hot pulverized coal refers to pulverized coalparticles at a temperature above 300 C.

The diificulties in pressurizing coal at such high temperatures arisefrom the fact that temperatures of 350 C. to 400 C. are above thesoftening temperature of bituminous coal. Therefore, pulverized coalparticles at such temperatures tend to agglomerate and stick together,forming a thick pasty mass. This problem occurs whenever hot pulverizedcoal is allowed to stand in a vessel, even at atmospheric pressure, andis greatly intensified when the hot pulverized coal is put underpressure. Using any method known in the art, any attempt to pressurizehot pulverized coal particles would result in the coal agglomeratinginto a semi-solid mass and hanging up in the pressurizing apparatus.

We have discovered a method whereby hot pulverized coal may beintroduced into a pressurizing chamber, put under pressure and deliveredfrom the chamber still in granular form, without any agglomeration orsolidification occurring.

The process of the invention comprises admitting the hot pulverized coalat atmospheric pressure to. a pressuretight chamber, sealing thechamber, diifusing through the coal an unreactive gas such as steam oran inert gas or a mixture of the two, while admitting the coal and whilebuilding up the pressure in the chamber to slightly above the pressurein the mixing chamber to which the coal is to be admitted, and thenopening the pressure chamber to admit the coal to the mixing chamber.

An apparatus of the invention comprises a pressuretight chamber havingan inlet means and outlet means for hot pulverized coal and inlet andoutlet means for steam or inert gas. The coal inlet and outlet means arestraight through construction valves, preferably of the clapper type.The various inlet and outlet means in the apparatus, with the exceptionof the aerating valve are all controlled so as to operate in a definitetime sequence, thereby acc'omplishing the pressurizing of the coal in amatter of minutes so as to permit semi-continuous operation. i

In the drawing:

Fig. 1 is a view of the entire apparatus, with the upper coal inletvalve A shown in section.

Fig. 2 is a section view of the lower coal valve B, showing constructiondetails common to all three coal valves.

Fig. 3 is a partial section of the upper part of the apparatus, showingthe operating mechanism for the lower coal inlet valve B.

The apparatus shown in the drawing comprises a pressure chamber 11 witha removable top 12 bolted thereto to form one pressure-tight chamber.

The hot pulverized coal which is to be pressurized is conducted to thechamber 11 through a supply pipe 13. It is admitted through two clappertype inlet valves A and B. The upper 'coal inlet valve A consistsessentially of an orifice having a flange 14 with smaller diameter pipe15 mounted therein and cooperating therewith a circular disc 16 mountedon a rotating rocker arm 17. The arm 17 is afiixed to a shaft 18 whichis held by brackets mounted inside the pipe section 19. The constructionand operation of this upper coal inlet valve A is otherwise identicalwith that of the lower coal inlet valve B through which the coal nextpasses. This latter valve is described in detail below.

While the hot coal is entering the chamber 11, an unreactive gas forinstance steam or an inert gas such as nitrogen, or a mixture of suchgases, is continually entering the chamber 11 through aerating valve 20.This steam or inert gas aerates the hot coal and forms a gas film aroundthe individual particles. This film forming action serves to prevent theparticles from agglomerating and sticking together. Thus the coalremains in the pulverized state and there is no formation of semi-solidmasses of the hot coal. The aerating valve 2t"; is kept open through allphases of the operational cycle because there is at least some hot coalin the chamber for all but a few seconds of the cycle, as will be seenlater.

When a full charge of hot coal has entered the pressure chamber 11through the two coal inlet valves A and B, these valves are closed toseal the chamber, except for the positive flow of gas through theaerating valve 20. The upper coal inlet valve A closes first, stoppingthe flow of coal, and a few seconds later the second valve B closes,effecting a pressure-tight seal. By employing two valves a better sealis etfected because the lower valve B does not close while coal ispassing through.

The pressure chamber 11 thus having been sealed with a charge of coalinside, the vapor valve 21 opens to admit a large volume of the aeratinggas. The pressure in the chamber is rapidly built up to a value of fromone-half to one pound above the pressure in the mixing chamber to whichthe hot coal is to be admitted. This latter pressure may be as low asone pound or as high as 50 pounds per square inch. Should it benecessary, even higher pressures could be obtained readily.

The three clapper-type valves A, B and C which admit the hot coal intoand out of the pressure chamber are all of the same general design andconstruction. A detailed description is given below of the lower coalinlet valve B, as shown in Figs. 2 and 3. The other two valves differonly in that they are mounted in sections of pipe rather than in thebody of the pressure chamber.

The lower coal inlet valve B is constructed as follows: An entrance pipe24 is mounted in a flange 22 which is attached to the upper end of thevessel 12. The end 23 of the entrance pipe 24 is preferably hardened ina suitable manner to resist wear and forms the valve seat. A disc 25,having a face similarly hardened, when in the closed position, as shownin Fig. 2, abuts against the pipe end 23 to stop completely the flow ofhot pulverized coal into the pressure chamber 11. The disc 25 is attached to brackets 26 attached by a pin 27 to a hinged member, an arm28, which in turn is attached to a rotating shaft 29, the shaft 29 beingheld pivotally by two brackets 31 attached to the inside wall of thepressure chamber 11. Thus, when the shaft 29 is'-rotated,;the

disc swings from the closed position-described above to,

an open position, through an arcofsomewhatmore than 90. When the disc isback, in-the open position, as.

shown in Fig. 1 of the drawing, the entrance pipe. 24.

mounted on the arm 28. The inner, surface of thehole through the arm 28through which ;the pin 21 passes is concavely rounded so as to permit asmall amount of movement in the otherdirection by the disc 25. Thesepivotal arrangements are for the purpose of allowing some;

compensating movement by disc 25in order to, effect a tight seal withthe pipe end 23.

The disc 25, being connected through the arm.28 .tov

the shaft 29, moves througha 90 degree are between the open and closedposition when the shaft 29 is rotated. The shaft 29 extends outside -thepressurized.cham ber 11, being supported outside by the support bracket32.

To prevent the escape of pressure from the pressure chamber 11, theshaft 29 passes out of the pressure chamber 11 through a packingfollower 33, held in a packing gland 34. This packing gland 34 holds alantern.

ring of packing material 35 around the shaft 29 to prevent pressureleakage. As a further safeguard, a positive pressure of inert gas isintroduced into the packing gland 34 through the inlet 36, from thesupply line 37.so as to prevent hot abrasive solids from getting intothe packing.

The outer end of the shaft 29, in the embodiment of the invention shownin the drawing, is connected to an air piston, though other drivingmeanscould be used.

A connecting arm 33 is shown fixed at one end totheshaft 29 andpivotally attached at the other to a connecting shaft 39. The connectingshaft 39 is in turn connected to the piston shaft 40 of the compressedair cylinder 41. The motion of the piston shaft 40- is suitablytransferred through the connecting shaft 39 and the connecting arm 38 tocause rotation of the shaft 29.

The movement of the piston shaft in and out of the cylinder 41 isdetermined by the flow of compressed air into the cylinder 41 which iscontrolled by the valve 42.

When the desired pressure in the chamber has been attained the vaporvalve-21 is closed and the-coal outlet valve C is opened and the chamberemptied of coal."

This valve C is then closed and an exhaust valve- 43 isopened, reducingthe pressure toatmospheric once more;

The coal inlet valves A and B are then opened, and the pressure chamberreceived another load of coal.

The construction and mode of operation ofthe coal H outlet valve Cisidentical with the-upper coal inlet valve A, and differs from the lowercoal inlet-valve B,-de-

scribed indetail above, only inthattherotating shaft is mounted in apipe 44 rather' than in the body 11.' A

thermocouple well 45 is provided for recording the temperature of thecoal in the chamber.

The operation of the invention is held closely to' a definite timesequence. The overall period for a pressurizing cycle may vary from oneto. twenty minutes,

depending on the size of the apparatus, the temperature of the coal, thepressure towhich-it-is to beraised and similar factors.

The cycle-to be described is of two; and

one-half minutes duration and was used toprocess-four tons ,of-coal perhour, the coal being at a temperature of 360 C. and being raised to apressure of 30 pounds...

amount. .The coal exit valve.C then opens and empties J the chamber inforty-five seconds. The coal exit 0 valve then closes, preferably with arapping action to clear the face and form a good seal.: The vaporexhaust valve 43 is then opened briefly to depressurize the chamber andcomplete the cycle. The chamber is now ready to receive a new load ofcoal. ,Throughout the cycle the aerating valve 20 is open and admittingaerating gas.

A pressurizing chamber, embodying the invention as shown in thedrawings, has been operated successfully on the time cycle justdescribed, receiving hot pulverized coal at atmospheric pressure and attemperatures of 350 Cato 400 C., and delivering it under pressures of 35to 40 pounds per square inch, still in the pulverized state and withoutagglomerated masses. provided by the introduction of the steam and inertgas through the hot coal, such operation would be impossible.-

While the valve used to admit and deliver the hot pulverized coal couldbe modified without exceeding the distinct advantages.

without the interference of solid particles. Preferably, the valveshould be located in a vertical or nearly vertical position. To preventwear of the seating surface, both the end of the pipe and the face ofthe valve disc may be hardened or otherwise treated by any suitablemethod to resist abrasion due to leakage of high velocity coal dustparticles.

A further advantage of the clapper-type valve shown is that the entrancepipe is a separate and removable part. Thus, entrance pipes with varioussized orifices may be substituted when desired, to control flow. Allparts of the valve are readily accessible for replacement and repair.

The apparatus embodied in the drawing is tilted at an angle from thevertical, which provides somewhat easier control of the coal flowthrough the apparatus, due to decreased velocity. The apparatus could becompletely vertical however.

not be greater than 30 degrees for the body of the ap paratus or for anyof the coal entrance or exit valves.

What is claimed is: 1. A method for pressurizing hot pulverized coalparticles which comprises introducing said hot coal particles into achamber at substantially atmospheric pressure;

sealing said chamber; introducing an unreactive gas into said chamberuntil the pressure within said chamber is between two to fifty poundsper square inch gage; removing said coal from said chamber under saidpressure; releasing the pressure from said chamber; and concurrentlyintroducing a further amount of unreactive gas into said chamber, atleast during said introduction of coal into said chamber and saidpressurizing of said chamber, for the purpose of preventing theagglomeration of said hot pulverized coal particles.

2. A method for pressurizing hot pulverized coal particles forintroduction into a mixing chamber which com-- prises introducing saidhot coal particles into a pressuriz ing chamber at substantiallyatmospheric pressure; sealing Without the aeration- In order not toexceed the angle of repose of the hot coal the angle with the verticalmustsaid pressurizing chamber; introducing an unreactive gas into saidpressurizing chamber until the pressure insaid p'ressurizing chamber isbuilt up to a selected value above the pressure in the mixing chamber towhich said hot coal is admitted, without agglomeration of the particles;delivering said coal from said pressurizing chamber to said mixingchamber under said pressure without agglomeration of the particles;releasing the pressure from said pressurizing chamber; and concurrentlyintroducing a further amount of unreactive gas into said pressurizingchamber, at least during said introduction of coal into saidpressurizing chamber and said pressurizing of said pressurizing chamberall without agglomeration of said hot pulverized coal particles.

No references cited.

1. A METHOD FOR PRESURIZING HOT PULVERIZED COAL PARTICLES WHICHCOMPRISES INTRODUCING SAID HOT COAL PARTICLES INTO A CHAMBER ATSUBSTANTIALLY ATOMSPHERIC PRESSURE; SEALING SAID CHAMBER; INTRODUCING ANUNREACTIVE GAS INTO SAID CHAMBER UNTIL THE PRESSURE WITHIN SAID CHAMBERIS BETWEEN TWO TO FIFTY POUNDS PER SQUARE INCH GAGE; REMOVING SAID COALFROM SAID CHAMBER UNDER SAID PRESSURE; RELEASING THE PRESSURE FROM SAIDCHAMBER; AND CONCURRENTLY INTRODUCING A FURTHER AMOUNT OF UNREACTIVE GASINTO SAID CHAMBER, AT LEAST DURING SAID INTRODUCTION OF COAL INTO SAIDCHAMBER AND SAID PRESSURIZING OF SAID CHAMBER, FOR THE PURPOSE OFPREVENTING THE AGGLOMERATION OF SAID HOT PULVERIZED COAL PARTICLES.